Islets of Langerhans have been isolated from normal rats and transplanted successfully into diabetic recipients. This results in the return to the normal state as measured by glucose tolerance testing and other parameters. Application of this technique to man is currently prevented by the requirement of immunosuppression and the relative inability to isolate human islets. This proposal covers a number of alternatives designed to bypass these obstacles. Included in these proposals are the development of transplantation chambers utilizing semi-permeable membranes to prevent rejection while permitting functional survival, the use of extravascular chambers to study rejection in vivo, and the development of a new islet culture technique which permits long term islet survival.